Production of hard metal alloys, especially for tools



Patented Sept. 5, 1933 PATENT OFFICE PRODUCTION or man METAL armors,ESPECIALLY FOR TOOLS m1 Schwarzkopf and Isidor Hirschl, Reutte, Tryol,Austria: said Hirsch! assignor to said Schwarzkopf No Drawing.Application November 16, 1931, Serial No. 575,482, and in Germany May28,

1931 4 Claims.

For the production of particularly efilcient,

hard tools, use is made of carbides of tungsten or molybdenum, which areprepared by fusing or sintering, and are thereupon pulverized and 5pressed into definite molds and subsequently highly heated. It hasprovedparticularly advantageousto add auxiliarymetals to the carbide,and then to sinter the whole, in order to obtain tool materials that arenot only extremely hard, but also tough.

In order to obtain tool elements of great hardness, the inventionemploys neither tungsten alone nor molybdenum alone, also nottungstencarbide or molybdenum-carbide alone,as suggested heretofore, buta mixture of one or more carbides formed irom one or more elements ofthe sixth group of the periodical system of the elements, comprisingmolybdenum, tungsten, chromium and one or more carbides of elements oflo the fourth group of the periodical system comprising titanium,silicon, zirconium.

Such carbides are not used, however, alone, but

in accordance with known principles they are employed with auxiliarymetals, principally those of I55 the iron group, such as nickel andcobalt, with some chromium, singly or in suitable mixtures.

The auxiliary metals are believed to increase the toughness of the alloyor tool produced without,

or practically without, changing the composition or structure of thecarbides present, although it might be that a kind of diffusion betweenthe auxiliary metals and the carbides, perhaps only in surface layers,takes place while they are heated at sintering temperature, and somekind of surface solution is formed therefore in the'hardened3 alloy.

A hard metal. tool element, according to the invention, contains fromabout 15% to less than carbide of one or more elements of the sixthgroup, and between about 15% to 39% carbide of one or more elements ofthe fourth group, the remainder being substantially auxiliary metal ofthe iron group, with or without chromium, the auxiliary metal amountingaltogether to from 45 about 3% to about 22%.

It has been found that surprisingly good results (for example, for highspeed material) are obtainable by using 30 to 15% molybdenum-carbide(MOzC), of the sixth group, and to 50 titanium-carbide (HQ with acontent of about 20% carbon), of the fourth group, adding hereto asauxiliary metals about 8 to 15% nickel and 0 to 7% chromium. Within thisrange the optimum seems to be at about 8 to 10% nickel and up to 55 1 to2% chromium.

For special other purposes (for example, slower speed material), amixture of titanium-carbide and molybdenum-carbide in about equalproportions, with auxiliary metal comprising nickel up to 9 and 15% andchromium up to 1 and 2%, has been proved. 1

Another mixture suitable for the purpose of the metalloids not beingreduceable by hydrogen and not, or only at high temperatures, formingcar-,

bides. Such oxides are, for example, alumina, silica. the alkalineearths, the group comprising zirconia, andthe group comprising the rareearth oxides. Particularly, the addition of alumina in the finestdivided form and in relatively small amounts, say up to about 0.5%}. hasenabled the formation of most suitable alloys of the herementionedvarious compositions.

Comparing a known alloy of tungsten-carbide with about 10% cobalt asauxiliary metal and an alloy of the present invention comprisingmolybdenum-carbide and titanium-carbide with nickel and chromium asauxiliary metals, the last-mentioned alloy containing, for example, 62%titanium-carbide, 27% molybdenum-carbide, 10% nickel, and 1% chromium,the hardness and toughness will surpass exceedingly that oftungsten-carbide with cobalt. It has been further found that bysubstituting in the last-mentioned alloy nickel and chrominum by cobalt,still better results are achievable than with the alloy containingtungsten-carbide and cobalt. Any suitable method may in itself be usedfor the production of the carbides and of the final alloy.

For producing molybdenum-carbide, the following way has proved mostconvenient. Metallic molybdenum and carbon are mixed in the proportioncorresponding to the theoretical values needed for producing thecombination M020.

This mixture is powdered. and then heated in a reducing atmosphere up toabout 1400 to 1600 C. Hereby the combination is produced containingabout 5.9% C., the rest being M02.

Titanium-carbide can be formed in a similar way from metallic titaniumand carbon, the temperatures used being, however, higher, as wellunderstood.

In similar ways, zirconium-carbide and siliconcarbide, etc., can beproduced.

Instead using solid carbon, also gaseous carbon can be used, forexample, in the form of carbon or carbon compounds containing gases ascoal gas, etc. Such gases are passed over the 5 finely divided metalpowders or metal compounds in carbon tubes at temperatures similar tomentioned before.

-The carbides so produced are then powdered again (if necessary) andintimately mixed with the chosen auxiliary metal or metals. Suitableproportions have already been mentioned. The mixtures are then preformedby pressing in suitable molds to a shape similar to the desired shape.Due allowance is, 01' course, made for the shrinkage which takes placeduring the following treatment.

The preforming in the molds may be done also under elevated pressure.

The body so preformed and advantageously still under pressure is now tobe treated to give it the dense and homogeneous internal structurerequisite to its service as a hard metal tool element. This is effectedelectrically by heavy current led through the body or through the mold.

Any other kind of heating may be employed. The temperature of the bodyis to be elevated to about 1400 to 1600 C.,.and this heat treatment isto be continued about one or more hours, or until the desired structure01' the body is obtained.

Another way consists in admixing with the powders ready for pretormingglycerine, glycol or other alcohols, pressing such mixture, convertingthe reagents at normal or elevated temperature, driving out totally theunconverted alcohol at about 120m 200 C., then working and finishingthis body of sumcient cohesion, whereupon the sintering is done.

The finished bodies or tool elements may be assembled with other partsto form the tool, or

those they may themselves directly constitute the tool.

It aluminium-oxide, or similar oxides, as mentioned before, are used asadditions in small quantities, then the crystals of heavy metal carbidecontained in the body are not materially changed or increased in size bythe heat treatment. The crystals areuniformly divided throughout "thebody. While, otherwise, some diflusion or solid solution takes placewithin several carbides and admixed auxiliary metals, such alloyingseems to be largely or entirely prevented by addition of the mentionedoxides. This helps to increase or to maintain the toughness of the mass.

It may be mentioned that in cases where oxygen is given oil during theheat treatment, such oxides may be obtained by adding to theinitialmixture the desired small amounts of the respective metals such asaluminum, silicon, etc., and having them combine with the oxygen i'reedduring the heat treatment.

What we claim is:

1. A. hard metal tool element comprising carbide of metal selected fromthe group consisting of chromium, tungsten and molybdenum andrepresenting from about over 15% up to less than about 50% of the body,and carbide of metal selected from the group consisting of titanium andzirconium, forming between about 39% and about of the body, and theremainder auxiliary metal selected substantially from-the iro group ofthe periodic system.

2. A hard metal tool element comprising carbide of metal selected fromthe group consisting of titanium and zirconium and carbide of a metalselected from the group consisting I of chromium, molybdenum, andtungsten, the content of carbide of the first named group being' fromabout 39% up to about 75%, the content 01' carbide of the second namedgroup being from about 15% up to about less than 50%, the remainderabout 5% to 22% substantially 0t auxiliary metal of the iron group.

3. Ahard metal tool element, containing substantially; titanium carbidefrom about 39% to less than 75% molybdenum-carbide between about 15% andless than 50% and the remainder nickel. 1

4. A hard metal tool element containing from about 60% to about 75%titanium carbide, about 20% molybdenum carbide, and the remaindersubstantially from about 5% to about 20% of auxiliary metal taken fromthe group consisting of cobalt, iron and nickel.

' PAUL SCHWARZKOPF.

ISDJOR HIRSCHL.

